Five civilians were wounded when several mortars hit Baghdad's heavily fortified Green Zone, which is home to several foreign embassies and government departments, an interior ministry official said.

Further north, in the northern city of Mosul, two Iraqi soldiers and two policemen were killed when their respective checkpoints came under fire from unidentified gunmen on Monday morning, police officials said.

The national elections next month is being billed as a critical test of Iraq's stability, following the withdrawal of US troops from cities and towns last year.

Both the Iraqi government and the US administration hope that Sunni participation in March 7 election would help end a bloody armed opposition launched by Sunni Iraqis after they boycotted the 2005 elections.

But the ban on candidates over Baath Party links has fanned Sunni fears of a plot by Iraq's Shia ruling parties to marginalise them again ahead of the vote.